Quote:
Originally Posted by j cAT
the recirculation door is moving by an electric motor. the control would be from the HVAC control module. could be the door gear tooth is broken.
so your sure it is vacuum controlled you checked these vacuum lines . the vacuum goes to the part you installed or you installed this with a electrical connector?
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The movement of the blend door is controlled by a small DC motor inside the actuator unit with a series of small plastic gears and the final drive gear has a small electric contact arm attached to it that is in contact with a round flat metal surface somewhat like a volume control knob. I would say this electric contact sends a signal to the computer telling it what position the blend door is in. There are no vacuum lines that control the movement of the blend door, It only has a small plastic clip plug that connects 4 wires to the actuator unit, I believe 2 of these wires control the small DC motor and the other 2 wires are for the computer to sense the position of the blend door. When I was talking about the blend door slamming to one side or the other by vacuum it did this when the actuator unit was removed from the heater housing and there was nothing holding the blend door and it could move freely, when the blower was turned on the flow of air from the blower would cause the blend door to slam shut to either side of the vent openings. If the blend door was closer to the left side vent when the blower came on it would be sucked shut to that left side vent and if it was closer to the right side vent when the blower came on it would be sucked shut to the right side vent. When the actuator unit is installed it prevents the blend door from moving freely, that is the actuator controls the position. I know the small drive gears in the actuator are not broken because, not only is the unit brand new, I took apart the old unit and there was nothing wrong with it and it made the same noise as the new unit. The noise it's making is not that of grinding or slipping plastic gears, the noise is the blend door itself moving to one side and shutting then moving to the other side and shutting (flip flop, flip flop, flip flop) The actuator is working but it is continually going back and forth not moving to one position and staying there like it is supposed to. Something in the computer or a switch in the heater controls or the position signal from the actuator is causing the blend door to go from outside air and then back over to inside air resurculation again and again. I read in a blog somewhere that another guy had this same problem and a chevy dealership told him he needed a new computer. If that's the case it's not worth the cost of replacing the computer but the constant flip flop noise is very annoying. I'm thinking of pulling the dash back out and disconnecting the wires from the actuator and if everything else still works good just leave it disconnected.